Physical, functional and chemical properties of Grewia venusta (ururu) mucilage extract

Food stabilizers and bulking agents required by food industries in developing countries are largely obtained by importation and usually at high cost. Attempts made to get other local substitutes have met with hydration, viscosity and syneresis problems. Grewia venusta (ururu) mucilage may be a possible substitute but it has not been explored. The objective of this study was to characterize this mucilage in terms of physical, functional and chemical properties. Grewia venusta stem bark obtained from Ajaokuta, Nigeria was subjected to aqueous extraction at tropical ambient temperature, oven-dried (thin layer, 50±3°C) and milled into powder. Its physical, functional and chemical properties were determined. Both the wet and dry mucilage (yield = 18%) were reddish brown in colour (L·=37.33, a·=9.38, b·=10.43). The dispersability and hygroscopicity were 93.00% and 14.00%, respectively. The apparent viscosity decreased from 7.68 to 6.23 Ns/m2 after drying. The mucilage exhibited higher shear stress values (3.84-5.90 Ns/m2) at 10°C compared to those (1.65-2.51 Ns/m2) at 80°C. The emulsion stability of the wet and dry mucilage was 17.72% and 16.40%, respectively. Foam capacity was low (8.00-10.39%) while foam stability was high (97.60- 97.78%). The mucilage contained 0.07% tannins, 0.21% saponins, 0.04% glycosides, 1.46% alkaloids, 0.06% flavonoids, 12.65% pectin, 0.92 mg/100 g oxalates, 0.10% hydrocyanic acid, 0.30% phytates and 0.88% oligosaccharides. These findings suggest that Grewia venusta mucilage has good potential use as a food additive.